<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
  </head>
  <body>
    <button id="btnStartSpan">Start Span</button>
    <button id="btnEndSpan">End Span</button>
    <button id="btnStartNestedSpan">Start Nested Span</button>
    <button id="btnEndNestedSpan">End Nested Span</button>
  </body>
</html>
